Injection molded thermoplastic spectacle lens suited for fully automated dip hardcoating

ABSTRACT

Plastic injection-compression multi-cavity molding of flash-free improved-cleanliness thermoplastic spectacle lenses ( 16 ) are suitable to be robotically dip hardcoated. Special spring-loaded ( 25, 26 ) molds having variable-volume mold cavities are used in an injection-compression molding process to form, without parting line flash, pairs of a wide range of differing optical power of polycarbonate Rx spectacle lenses ( 16 ). These pairs have special molded-on design features which are specially suited for full automation, starting with a novel way for ejection out of the mold into a takeout robot which is integrated via full automation with subsequent dip hardcoating. A molded-on tab with each pair of lenses is specially suited for manipulation by SCARA type robot. This combination produces micro-clean hardcoated paired molded lens made entirely within a single continuous cleanroom air enclosure surrounding the lenses, without any human operators therein, nor requiring any cutting or trimming of the molded paired lens or runner system before hardcoating, nor use of Freon (tm) CFC nor aqueous cleaning protocols before dipcoating.

RELATED U.S. APPLICATION DATA

This application is a Division of application Ser. No. 08/795,903, filedFeb. 5, 1997, now U.S. Pat. No. 5,750,060, which was a Division ofapplication Ser. No. 08/795,613, filed Feb. 5, 1997, now U.S. Pat. No.5,750,156, which was a Division of application Ser. No. 08/533,126,filed Sep. 25, 1995, now U.S. Pat. No. 5,718,849.

FIELD OF THE INVENTION

The field of the present invention is plastic injection-compressionmolding of pairs of flash-free improved-cleanliness thermoplasticspectacle lens, to be fed into subsequent in-line dip hardcoating. Morespecifically, a method and apparatus for multi-cavity injection moldingof polycarbonate spectacle lens is integrated via full automation withdip hardcoating, to produce clean hardcoated molded lens made entirelywithin a single continuous cleanroom air enclosure surrounding thelenses, without any human operators therein, nor requiring any cuttingor trimmings of the molded paired lens or runner system beforehardcoating, nor use of Freon (tm) CFC nor aqueous cleaning protocolsbefore dipcoating. An extension of this cleanroom enclosure and robotichandling may optionally provide in-line continuous-product-flowautomatic inspection of optical power and lens cosmetic quality, and/ormay optionally provide in-line continuous-product-flow anti-reflectivethin film vacuum coating, before the molded-and-hardcoated polycarbonatelenses exit out of the continuous cleanroom air enclosure and/or receivemanual handling.

BACKGROUND OF THE INVENTION

A. Rx Lens Market Trend to Polycarbonate

The relevant product field is vision-corrective plastic ophthalmicprescription spectacle lens (hereinafter abbreviated “Rx lens”) havingrefractive index greater than 1.530 glass and 1.49-1.50 “CR-39”(chemically, peroxide-crosslinked allyl diglycol carbonatethermoset-cast lens). This is the fastest growing category of Rx lensmaterials in the last five years, both in U.S. and worldwide markets.Such cast thermoset and injection-molded thermoplastics are so highlydesirable because the consumer/wearer of spectacle lens finds them to bethinner (due to greater light-bending power of high-refractive-indexplastic) and lighter (lower specific gravity, particularly in the caseof polycarbonate versus CR-39). As a result, the myopic (“near-sighted”)spectacle lens wearer can avoid the cosmetically undesirable appearanceof “wearing coke-bottle glasses”. In addition, lighter weight meansbetter comfort, less weight, less pinching at the nose and top of ears,where the loadbearing surfaces are.

Within this “thin & light”, higher-refractive-index plastic Rx lenssegment, U.S. market statistics show a combined share of 25-30% of thetotal market. However, within this segment, the thermoset casthigh-index share has been essentially unchanged since 1991; nearly allthis growth in recent years is of the thermoplastic injection-molded Rxlens type, most specifically embodied by polycarbonate (R.I.=1.586).(Although there are other candidate high-index thermoplastics also beingconsidered, so far polycarbonate is most firmly establishedcommercially—hereinafter, “polycarbonate” will be taken to be inclusiveof other optical-grade thermoplastic substitutes, as would be obvious tothose skilled in the art).

The major reason for market share shift toward polycarbonate Rx lens andaway from cast thermoset high index Rx lens is reported to be theconsiderably lower manufacturing costs of polycarbonate Rx lens at highproduction volume levels. This, in turn, is from the high levels ofautomation attainable with polycarbonate, but inherently not attainablewith the more labor-intensive thermoset casting operations. Atlow-volume percent utilization, highly automated production can beburdened with extremely high fixed cost, but as volume increases past“breakeven” levels, there is a cross-over point where the relativelyhigher variable-cost inputs of labor and materials inherent to thermosetcasting becomes very disadvantageous. Thereafter, with increasingvolume, the incremental profit per unit of increased volume becomeshighly leveraged in favor of the more automated (polycarbonate)manufacturing operation.

This is reflected in market pricing from the lens manufacturers, whereinthe cast high-index hardcoated Rx lenses are far from beingprice-competitive with corresponding prescriptions of the multi-cavityinjection-molded, hardcoated polycarbonate Rx lenses (especially,finished single vision (“FSV”) types which have higher unit salesvolumes per Rx). The cast high-index RSV can be typically 50-100% higherpriced. It is for these reasons why a further level of manufacturingcost reduction, through even greater level of automation and throughimproved capital efficiency (=lower breakeven volume, which reducescapital requirements for new manufacturing entries into the field) willbe strategically crucial in the polycarbonate Rx lens' future growth.

B. Prior Art Patents on Multi-Cavity Lens Molding and Dip Hardcoating

Today, polycarbonate Rx lens worldwide production is dominated by fourcompanies, together comprising an estimated greater-than-90% share ofworld market (although there are new entries just starting up). Each ofthese four currently employ some form of injection-compressionmulti-cavity molding process and apparatus, at the start of their “batchprocess” manufacturing flowsheet (see FIG. 4A Comparative Example). Thenext step is post-molding cutting of runner system and/or degating ortrimming off ejector tabs, so the trimmed lenses can be mounted into alensholder rack. Typically, these are semi-automatic operations assistedby a human operator, but they can also be entirely manual operations. Anexample of a molded-on hanger tab which is fitted to engage a Lensholderrack holding a plurality of such lenses is shown in Weber (U.S. Pat. No.4,443,159). The next step in the manufacturing flowsheet is to use someform of cleaning protocol (earlier versions were all Freon (tm) CFCultrasonic vapor degreaser methodologies; more recently, water-basedcleaning is aqueous high-pressure sprays with centrifugal spinning, ormulti-stage ultrasonic tank immersions, followed by drying operations).These cleaned and dried lenses are then dipcoated in liquid hardcoatingsolutions (either heat-curing silicone types or UV-curing types), andthe coating is cured by chemical crosslinking.

Two of the above-mentioned four polycarbonate Rx lens manufacturers arelicensees of Applicants' U.S. Pat. No. 4,828,769 and U.S. Pat. No.4,900,242. A third is Gentex Corporation, assignee of Weymouth (U.S.Pat. No. 4,933,119). A fourth is Neolens, assignee of Bakalar (U.S. Pat.No. 4,664,854). These patents employ some form of injection-compressionmolding process sequence with a plurality of mold cavities and employingvarious means for achieving cavity-to-cavity balance therebetween. Thesethree patents employed by four manufacturers differ in how the moldedlens is ejected out of the lens mold, as can be easily seen by observingthe O.D.-perimeter lens edge & sidewall of a sample lens from eachmanufacturer. More on this later in FIG. 2 and its descriptive text. Allthree necessarily do at least some cutting before dipcoating ispossible.

Looking at other prior art patents showing multicavityinjection-compression molding of Rx lens, Weber (U.S. Pat. No.4,008,031) apparatus for injection-compression molding of Rx lens showswhat appears to be a two-cavity mold. At 180 degrees opposite the gateinlet 23 is a hanger 20 for use in subsequent dipcoating operations.Weber also shows two molded-on ejector tabs 16, located at about10:30-1:00 o'clock positions, with respect to the gate/dripmark locationat 6:00 o'clock. Normally, this location would have the detrimentaleffect of propagating coating flowout runs along the front and backfaces of the molded lens during dipcoating withdrawal, but in Weber'scase, he has installed the hanger tab and ejector tabs onto acircumferential flange 12, which is set back from both the front andback lens edges, such that coating flow runoff could then follow thisflange from top to bottom of each individually-held lens (provided thelens don't swing from side to side).

Uehara et al (U.S. Pat. No. 5,093,049) also teaches and showsinjection-compression molding of Rx lens in a two-cavity mold, with thecavities connected by a cold runner and sprue, with the sprue being ableto be mechanically shut off at a predetermined time in the cycle, toprevent backflow. Uehara is silent on any ejection means for demoldingthese two lenses and no ejector tabs or pins are shown. If the forwardtravel of the movable cores, which provide the compression, is limitedby hard stops, they cannot be used to drive forward past the partingline once the mold is open, to assist ejection. In that case, a humanoperator would be relied upon to manually grasp the cold sprue and pullloose the two lenses attached thereto from the mold. No hanger tab isshown or mentioned.

Other historically important injection-compression molding of Rx lensesincludes Spector et al (U.S. Pat. No. 4,836,960) and Laliberte (U.S.Pat. No. 4,364,878), but both of these are limited to single-cavityembodiments.

Looking now at Rx lens dipcoating prior art patents (in additioon topreviously-cited Weber (U.S. Pat. No. 4,443,159), Laliberte (U.S. Pat.No. 3,956,540 Method and U.S. Pat. No. 4,036,168 Apparatus) teaches aform of conveyorized transfer of such lensholder racks through amultistation machine internally having a filtered-air cleanroomenvironment, wherein the lenses are successively ultrasonically cleanedand destatisized, then dipcoated, then dried and at least partiallycured to a tackfree state before the conveyor takes them to aloading/unloading station, where the lenses can be removed by theoperator. Similar configurations were developed using differentautomated transfer means, including two chain-drive conveyors operatingin parallel and connected by crossbars whereon the lensholder rackswould be hung, or, alternatively, an overhead conveyor with power andfree flights for indexing could be used, with suspended removablelensholder racks mounted thereon. Such configurations for polycarbonateRx lenses (and non-Rx lenses) typically used at least one (preferably,two, in series dips) Freon ultrasonic cleaner/degreasers, wherein thepolycarbonate lenses were immersed in the ultrasonic sump for aprescribed time, during which cavitation (generation and collapse ofmicroscopic bubbles) provides high kinetic energy workingsynergistically with the Freon's solvency (to reduce adherent filmsholding onto the soils on the lens surface), to thus dislodge and floataway surface contaminants of both soluable and insoluable types. Afterlens removal from the ultrasonic sump solution, an azeotropicfreon/alcohol vapor zone would help rinse and dry the lens before goinginto the dipcoating tank.

Liebler et al, UK Patent Application GB2 159 441 A, published Dec. 4,1985; assignee: Rohm GmbH) also teaches continuous dip production ofscratch-resistant liquid coatings onto plastic optical moldings (such aslenses). It specifically teaches an endless conveyor belt to transferlensholder racks-containing a plurality of lenses. Among the opticalplastic moldings contemplated are spectacle lenses, and FIG. 2 shows amolding with a “lug 10 for clamping purposes is formed thereon anddiametrically opposite this lugged end is a dripoff lug 11, so thatexcessive scratch-resistant coating composition can drip off withoutforming a ridge when coated and dried.” (Lines 97-105). In comparison toLaliberte, this machine is far simpler, contemplating merely aload/unload, a liquid dipcoating station, and a drying station shown(described as, “preferably, two or more infrared radiators”. Not shownbut mentioned in text is . . . “cleansing bath may also be providedupstream of the immersion bath. The cleansing bath may, for example, bean ultrasonic bath containing organic solvent”. (Lines 122-128).However, Liebler is believed not to have ever been actually used forspectacle lens coating nor Rx lens coating. There are major technicalproblems unforeseen by Liebler. His FIG. 2 lens withdiametrically-opposed hanger tab and drip tab would inevitably havecoating flowout runs propagated from the two junctions of the coatingtab, at its shoulders. Unfortunately, these runs take place in the veryworst location of the perimeter, since the coating flow runs will godirectly through the central, most critical zone of the optics forvision (see Comparative Example FIG. 2D). To the extent that the Lieblerapparatus might be acceptable, it would not be believed to be spectaclelenses, but rather ordinary protective-covering lenses such as watchglasses, scales, and mirrors, none of which are required to have thehigh quality of image transmission that corrective-vision spectaclelenses must have. Where the hardcoating merely is to protect from heavyscratching and the protective-covering lens is merely to provide sometransparency to a product or device, such flow runs may be harmless andnot a functional problem. However, for spectacle lenses with humanvision problems resulting from optical aberrations, such coating flowruns would be completely unacceptable and the source of very highpercent rejectable flaws. If such tab configurations are as shown, ofthe full thickness of the lens molding, then such a problem would beabsolutely intrinsic. However, if the tab is not of the full thicknessof the lens, as shown in the Weber drawings, but merely thick enough tosupport the relatively light weight of the lens suspended thereby, thensuch a tab location would be acceptable, but only if the lens is heldlevel in its mount, not rocking back,;and forth, which would be aanother problem envisioned with Liebler's “endless conveyor”.

C. Environmental and Economic Problems with Lens Cleaning

“Freon” cleaning is based upon now-unacceptable CFC-113(ozone-depleting), production of which theoretically ceased on Dec.31st, 1994, in accordance with the Montreal protocol and its Eurevisions. As a result, new Rx lens installations necessarily havesubstituted aqueous cleaning approaches instead. One such approachemploys high-pressure (up to 20,000 psi) jets of water spray which arescanned across the front and back surfaces of the lens, by moving thelens (such as spinning it on a spindle) or by moving the spray head(such as by reciprocating motion) or preferably, a combination of both.High-pressure water spray is very effective in removing insolubleparticulate forms of surface contamination (such aselectrostatically-held polycarbonate dust particles or airborneinorganic dusts) but has the drawback that such cleaning is 100% “lineof sight”, so not only must lenses typically be cleaned one at a time,but a typical spin/spray combination requires one side to be cleaned,then manually or robotically flipped over and placed back on a differentspindle to clean the second side. The throughput of such equipment(number of lenses per hour) versus the labor cost and capital cost isvery much higher than the old Freon cleaners it replaced, which are nowenvironmentally unacceptable.

A second way of aqueous cleaning is to have an ultrasonic, water-baseddetergent solution in the first stage of a countercurrent-flow,multi-station, automated cleaning line with conveyorized transporttaking the lenses through successive immersion tanks (typically, atleast five, and preferably 7-15 stations, including deionized waterrinses).

Whether by high-pressure water spray or by ultrasonic, multi-stage tankimmersions, the resulting clean-but-still-wet polycarbonate lens cannotyet be dipped into the liquid hardcoatings (which are all chemicallyincompatible with any significant % water), so they still face anotherproblem, and that is how to completely remove all the remaining waterfrom the lens (and/or its lensholder rack), without creating superficialstains (“water spots”) on the lens' optical surfaces. In the case ofwater-immersion tanks, the last tank is typically maintained at a veryhigh temperature, near the boiling point of water (which can cause lens“fogging” due to high % humidity inside the cleanroom wherein dipcoatingdrydown must also be done), and the withdrawal rate of the lenses beingremoved from the tank is extremely slow, to encourage capillary effectto maximize water removal. In the case of spin/high-pressure spray,(centrifugal action of high-RPM spinning speeds is attempted to slingoff all excess water. Nevertheless, because the liquid hardcoatingsolutions cannot stand even small amounts of water “dragout” introducedby lenses (even small droplets of water will result in streaky or spottyfogging of the coated lenses or blotchy appearance). So, inevitably, ahot-air-circulating dryer (filtered for cleanliness) must be used, whichmakes for an energy-intensive and costly operation. The multi-stationautomatic-transfer water cleaner in-line system takes up a great deal offloor space and costly (multi—$100,000). In addition, disposal of theliquid effluent from these aqueous cleaning solutions is turning out tobe an environmental problem not previously encountered with the Freoncleaners it replaced.

OBJECTS OF THE INVENTION

For these reasons, one objective of the present invention is to producecleanly-demolded multicavity Rx lenses which are ready to dipcoatwithout cutting or trimming, nor any use of Freon or aqueous cleaningprotocols, with a molded-on hanger tab having special design suited forrobotic handling and transfers.

Another objective of the present invention is to have no human operatortouch the lenses, starting from the time that multicavity demoldingstarts until after the hardcoating is at least partially cured to atackfree state. Preferably, for minimal airborne contamination, no humanoperator will even be inside the same cleanroom airspace which surroundsthe lens from start of demolding until after the hardcoating is at leastpartially cured to a tackfree state.

Another objective of the present invention is to increase productivityby changing the “unit of transfer” being handled from individual Rx lensof the prior art to paired molded-together Rx lens, which come from themold ready to be robotically handled by means of the molded-on hangertab having special design.

Another objective of the present invention is to minimize any plastic“flash” at the parting line edges of the paired molded lenses, so as toprevent dipcoating flow runs propagated off such flash and/or toeliminate any trimming off of flash before dipcoating, since suchtrimming processes generate plastic airborne particulate contaminations.

Another objective of the present invention is to be able to demold thelens cleanly, with ejection processes generating minimal (or none) metalor plastic airborne particulate contaminations.

Another objective of the present invention is to further reducemanufacturing costs of Rx polycarbonate lenses by improved % yields,less work-in-process inventories, and better labor productivity by thisnovel fully-automated continuous-process flowsheet vs. prior artbatch-process flowsheet.

SUMMARY OF THE INVENTION

The present invention employs “design for manufacturability” principlesfound lacking in the prior art. An essential element of the presentinvention is that the unit of transfer, from the demolding step onthrough the coating-and-curing step, should be a pair of Rx lenses, notindividual Rx lenses. Thus, each time a robotic transfer takes place,output is effectively doubled in this way. This insight is not found inthe prior art, which teaches and shows only one single lenses per tab.

A second element is to provide means for a flash-freeinjection-compression molding process, using 2-stage spring-loadedforces which determine the cavity height of variable volume moldcavities during the filling and the ejecting phases of the cycle. (Asused herein, “parting line flash” means plastic spilled out of themoldset along the parting line where the A side and B side of themoldset joins). Since any plastic “flash” at the parting line edges ofthe paired molded lenses is most likely to occur in the last fractionsof a millimeter of the “mold-closing” compression stroke during such afilling process, this element greatly increases the spring forces whichhold the moldset's parting line shut only during this lasthalf-millimeter of compression stroke. Eliminating flash preventsdipcoating flow runs which readily propagate off such flash and/or toeliminate any trimming off of flash before dipcoating since suchtrimming processes will generate plastic airborne particulatecontaminations.

A third element is novel demolding operations which minimize oreliminate generation of airborne particulates which can contaminate themolded Rx lens product. This element first is embodied into Rx lensproduct design, most specifically, the lens edge detail geometry.Secondly, apparatus considerations must be built into the mold design toprovide the required process steps of automatically stripping moldedpaired Rx lens off, when the mold is fully open and a robot arm withsuitable gripper jaws is in its proper location to receive the ejectedpaired molded Rx lens (no manual assistance is to be needed duringdemolding.)

A fourth element of the present invention is elimination of all cuttingor trimming of solidified thermoplastic once demolding has occurred,until after dipcoating has been applied and cured at least to a tackfreestate. Eliminating flash by improved molding process (by the 2-stagespring force) is better than trimming flash off later. Any ejector tabsor drip tabs must be suitably located along the lens perimeter so as notto interfere with proper dipcoating and not to propagate coating flowoutruns. Specifically, no such tabs will be placed in the upper 90-degreequadrant (defined as 10:30-1:30 o'clock locations) of the lensperimeter. The molded paired Rx lens must be connected therebetween by acold runner, with said runner located in the 1:30-4:30 o'clock sidequadrant for to the left lens and the 7:30-10:30 o'clock side quadrantfor the right lens.

A fifth element of the present invention is an integrally-molded hangertab, typically located substantially equidistant between the two lensesin the molded pair and rising substantially vertically off of thecold-runner connecting the paired lens (such symmetry has the advantageof minimizing side-to-side tilting of the paired lens). In an opticalbut preferred embodiment, the head of this molded-on hanger tab will beabove the highest top edge of the molded pair when held vertically, soas to prevent the liquid dip hardcoating from contacting the roboticmeans for gripping the head, so the stem length between the head and thecold runner should be at least sufficiently above said top edge of lens.Most preferably, the stem will be sufficiently longer so that a secondgripping position with protruding slide-stop can be located also abovethe top edge of the paired lens. (In an alternative optional butless-preferred embodiment, the head of this molded-on hanger tab will bebelow the highest top edge of the molded pair when held vertically, usedwith periodical clean-off of the accumulated dip hardcoating which hascontacted and cured onto the robotic means for gripping the head.)Special features are designed into the head so as to geometrically matewith certain robotic devices, workholders and racks.

Optionally, a drip tab is located in the bottom quadrant of each lens(4:30-7:30 o'clock positions), to minimize dipcoating dripmark size, bycapillary wicking action to drain off excess liquid coating once themolded paired lens have been fully removed from immersion in thedipbath. These optional drip tabs would, however, have the disadvantageof requiring a trimming operation after coating is cured, and also theywill increase polycarbonate resin usage+cost per lens.

These four elements of the present invention enable multi-cavityinjection molding of polycarbonate spectacle lens to be integrated viafull automation with dip hardcoating, to produce clean hardcoated moldedpaired lens made entirely within a single continuous cleanroom airenclosure surrounding the lenses, without any human operators therein,nor requiring any cutting or trimming of the molded lens or runnersystem before hardcoating, nor use of Freon CFC nor aqueous cleaningprotocols before dipcoating. The novel combination of Applicants'lensmold processes and apparatus and molded lens design for themanufacturing processes contribute to this end. An extension of thiscleanroom enclosure and robotic handling may optionally provide in-linecontinuous-product-flow automatic inspection of optical power and lenscosmetic quality, and/or may optionally provide in-linecontinuous-product-flow anti-reflective thin-film vacuum coating, beforethe molded-and-hardcoated polycarbonate lenses exit out of thecontinuous cleanroom air enclosure and/or receive manual handling

Another novel improvement using a special spring-loaded assembly of 2different types of springs has been shown to reduce parting line flashin variable volume injection-compression molding process, applicable toany edge-gated molded plastic article.

DESCRIPTION OF DRAWINGS

FIGS. 1, 1A and 1B show a two-cavity Rx lens mold of the presentinvention, in 2 cross-sectional split views (showing different stages ofmolded lens formation and ejection/demolding steps within a singlemolding cycle) and in a plan view.

FIGS. 2, 2A, 2C and 2D shows comparative examples from selected priorart, with special attention paid to location of dripmark and ejectortabs or gates that need to be cut before dipcoating can take place, aswell as orientation of hanger tabs.

FIGS. 3, 3A, 3B, 3C and 3D show the paired molded lenses after ejection,with preferred hanger tab location and stem length, and specific headand stem configurations of the present invention suited for mating withdifferent variations of robotic gripping position and workholder matinggeometries.

FIGS. 4A, 4B, 4C and 4D shows manufacturing flowsheets, with the processsteps shown in block diagram, and those steps which are to be donerobotically within a cleanroom are shown within dashed-line boxes.

DETAILED DESCRIPTION OF THE INVENTION

A. Lens Formation and Ejection within Moldset.

The present invention employs a novel and advantageous method andapparatus for ejecting multi-cavity injection-compression-molded Rxlens, in molded pairs each with a hanger tab (see FIG. 3), whilepreserving cleanliness of both the demolded paired lenses and theoptically polished molding surfaces of moldset, free of metal or plasticparticles. Refer to FIGS. 1, 1A and 1B, showing a simplified two-cavitylens moldset, with the injection molding machine nozzle tip (not shown)injecting into a cold sprue bushing (9) and cold runner system (15)which is centered between the two mold cavities. An optional butpreferred embodiment for molding two or more pairs of Rx lenses duringone cycle of a single moldset would employ instead a hot-runner systemusing a plurality of hot-runner nozzle tips in place of the singleinjection molding machine nozzle tip which injects into cold spruebushing (9) and cold runner system (15); such a hot-runner apparatus fora four-cavity mold is shown in Applicants' U.S. Pat. Nos. 4,828,769 and4,900,242 (incorporated herein by reference), FIG. 17. Anotheralternative hot-runner system for optical thermoplastic molding is shownin Applicants' U.S. Pat. No. 4,965,028, incorporated herein byreference. A cold well (40) is advantageous to build into the cold sprueand cold runner system, to trap “cold slugs” before they reach the lensmold cavities. Note that a slight undercut (41) or negative draft angleon cold well (40) will provide a positive mechanical retention force,which is helpful later on in ejection steps.

Another optional but preferred embodiment for molding pairs of Rx lenseswithin a single moldset would employ “variable volume” mold cavities,wherein the initial cavity height dimension is larger before injectionstarts than the final molded lens thickness dimension. Such a “variablevolume” mold cavity moldset apparatus typically uses aninjection-compression molding process sequence to mold the Rx lens,wherein a driving force squeezes the injected melt sometime afterinjection starts to reduce this cavity height dimension (refer to citedprior art lens molding patents for various schemes for driving forcesand sequences). A preferred one shown in Applicants' U.S. Pat. Nos.4,828,769 & 4,900,242 employs a resilient member 13 (such as a hydrauliccylinder or a mechanical spring) of FIG. 10B to determine the cavityheight dimension, so that when the resilient member 13 is extended oruncompressed, the cavity height dimension is larger, by a compressionstrokelength 40 dimension, and when the resilient member 13 iscontracted or compressed (such as by increased mold clamping forcesexerted by the injection molding machine squeezing the platens together,most preferably before injection is completed), the cavity heightdimension is made smaller by making the compression strokelength 40dimension become zero. See FIGS. 2-8 which show this injectioncompression process sequence throughout one complete molding cycle.

It has been found by Applicants since that patent was filed that use ofhydraulic cylinders for the resilient member 13 within polycarbonate Rxlens molds is disadvantageous, since such moldsets run at very hot(240-295° F.; 120-150° C.) temperatures, causing seals to leak and oilto contaminate the partforming surfaces. Use of conventional coil-typedie springs as resilient member do not have that problem, and arelong-lived, and can give the long compression strokelengths (as high as0.400″ or 10 mm has been used to mold very high minus power Rx lens with1.0-1.5 mm lens center thickness with 10-14 mm edge thicknesses withminimal “knitline”). However, they have flash problems duringmoldfilling; to eliminate parting line “flash”, the spring force holdingthe parting line shut must exceed the force of melt pressure beingexerted upon the projected area wetted by melt, and within the last0.1-0.5 mm of the compression stroke is when typically such flashing canoccur. Parting line “flash” (plastic spilled out of the moldset alongthe parting line where the A side and B side of the moldset joins) mustalso be eliminated or minimized, as it will otherwise be trimmed offbefore dipcoating (thus generating particulates) or it may create liquiddipcoat flow runs. Use of extremely stiff, high-deflection-forceconventional coil-type die springs as resilient member to solve thatproblem create a different problem during the ejection phase of themolding cycle, however, since as soon as the clamping force is releasedin preparation for mold opening, these high spring forces act as acatapult for the lenses and cold runner by prematurely pushing forwardthe parting line molding surfaces before the injection molding machine'sejection mechanism is actuated.

The present invention preferably can employ a novel combination of 2different types of moldsprings within the moldset to give “2 stage”workings of these “resilient members”. As shown in FIG. 1, (shown insplit cross-sectional view when the spring is uncompressed, such as byreleasing mold clamping forces exerted by the injection molding machineduring ejection phase of the cycle), a conventional coil-type steel diespring (25) having long compression strokelengths but moderatedeflection force are used in combination with extremely stiff, very highdeflection force stack of Belleville spring washers (26) held in placeby shoulder bolt (29), to give 2 different levels of moldspring forcesduring 2 different phases of the strokelenght—when either initialmold-opening or-final-closing movements are in the 0.0 to 0.5 mm range,the very high deflection force stack of Belleville spring washers (26)dominate from then on, the weaker coil-type die spring (25) are the onlyapplicable spring force, giving a controllable mold-opening stroke (toohigh spring forces can then almost “catapult” the paired molded lensesoff the B side, held on only by retention (41)). Together, theydetermine the variable volume cavity height dimension, on each moldingcycle to create a compression strokelength (21), up to a maximumdimension determined by shoulder bolt (29) In such an optional butpreferred embodiment of the present invention, this injectioncompression process sequence is as shown in Applicants' U.S. Pat. Nos.4,828,769 & 4,900,242 FIGS. 2-6, but differ thereafter (not as shown inFIGS. 7 & 8), in how the Rx lenses are to be de-molded and ejected. Fora flash-free injection-compression mold filling process, using 2-stagespring-loaded forces greatly increases the spring forces which hold themoldset's parting line shut, only during this last half-millimeter ofcompression stroke. This process automatically changes the sum of the 2springs' force just when greater force is needed, in the last fractionsof a millimeter of the “mold-closing” compression stroke during such avariable volume mold filling process.

Applicants' 2-stage springload combination (stiff-spring applied only ashortstroke+soft-spring applied over the whole longer stroke) is animproved form of “resilient member” operating within any suchvariable-volume injection compression mold in which the cavity height isdetermined by the degree of elongation of springs. A review of the priorart cited herein and cited in Applicants' U.S. Pat. Nos. 4,828,769 &4,900,242 shows no such 2-stage springload combination, nor any suchinsight into the benefit thereby. Specifically, any edge-gated plasticarticles to be molded within a variable-volume injection compressionmold in which the cavity height is determined by the degree ofelongation of springs will have the same tendency toward parting lineflash, and the larger the projected area of the cold runner system(especially if large fan gates or full-length runner-gating is used),the worse the flash problem will be. If the article is flat and meltflowpathlength is short, then a very short (0 to 1 mm) compressionstrokelength can be used, for which a single very stiff spring geometryis satisfactory, so Applicants' novel 2-stage springload combination isthen unnecessary. However, if the article is of non-flat contour andmeltflow pathlength is longer, then a longer (>1 mm; typically 2-10 mm)compression strokelength must be used, for which a single very stiffspring geometry is unsatisfactory, Applicants' novel 2-stage springloadcombination is then useful and necessary, to control flashing tendency.Such other articles may be other precision optical lens products (suchas light-amplifying LCD lens arrays for flat panel displays, manyoptically microstructured surfaces replicated through molding including“binary optics”, “hybrid optics”, fresnels and holographic imaging) andmolded automotive windows, headlamp lenses, and mirrors, but flashfreenon-optical opaque injection-compression moldings of similar geometriesis also contemplated, such as large auto exterior body panels (hoods,doors and fenders) and in-mold-textile-surfaced interior panels. Allthese non-spectacle-lens applications are known to have considered orused variable-volume injection compression molding, and the flashproblem is believed to have detered some from actual use. Applicantshave recently run such variable-volume injection compression molds withand without the novel 2-stage springload combination, and these testshave proven clearly the anti-flash benefits claimed.

Such an injection-compression molding process for reduced parting lineflash on at least one molded thermoplastic article operates within amoldset mounted within an injection molding machine having programmablecontrol of means for applying clamping forces and opening forces onto aparting line formed between A side and B side of the moldset, and theinjection molding machine has programmable control of means for movingforward or back an ejector assembly within the B side of said moldset.The moldset has at least one edge-gated variable-volume mold cavityhaving partforming surfaces on opposing paired A side insert and B sideinsert facing the parting line, and at least one extendable andcompressible passive resilient member of varying length determines acavity height dimension of the mold cavity within preset mechanicallimits. The resilient member being an operative combination of:

-   -   i) steel coil die spring to provide a moderate spring force over        a very long distance in a first clamping position of the        moldset, with    -   ii) stacked Belleville type steel spring washers to provide a        very still spring force over a very short distance in a second        clamping position of said moldset,        with the resilient member being mounted between the B side        parting line mold plate and B side clamp plate of said moldset,        and exerting combined spring forces to bias forward the B side        parting line mold plate toward the parting line. In the        injection compression molding process,    -   when there is less clamping force exerted by the injection        molding machine than a first spring force equal to the steel        coil die spring force acting alone to bias forward the B side        parting line mold plate toward the parting line, the resilient        member length will be a maximum within the present mechanical        limits in a first clamping position of the moldset, and    -   when there is more clamping force than the first spring force        equal to the steel coil die spring force acting alone to bias        forward toward the parting line but less clamping force than a        second spring force equal to the steel coil die spring acting        together with steel spring washer force to bias forward the B        side parting line mold plate toward the parting line, the        resilient member length will be an intermediate value in a        second clamping position of the moldset, and    -   when there is more clamping force than the second spring force        equal to the steel coil die spring acting together with steel        spring washer force to bias forward the B side parting line mold        plate toward the parting line, the resilient member length will        be a minimum within the preset mechanical limits in a third        clamping position of the moldset.

This process has the steps of:

-   -   a.) Pre-enlarging the mold cavity by substantially closing a        perimeter of the mold cavity at the parting line so as to        prevent molten thermoplastic from flashing, in a first position        of the moldset formed by applying a clamp force equal to a first        spring force, such that a first cavity height equal to the sum        of the desired compression strokelength plus a final thickness        of the molded article is determined, before injection starts;    -   b.) Partially filling the mold cavity after injection has        started by progressively reducing cavity height in a second        position of the moldset formed by increasing clamp force applied        to exceed the first spring force but less than the second spring        force;    -   c.) Completely filling said mold cavity after injection has        ended by further progressively reducing cavity height to reach a        third position of the moldset formed by increasing clamp force        applied to exceed the the second spring force;    -   d.) Cooling said molded article within the mold cavity after        injection has ended by maintaining cavity height substantially        at the third position of the moldset formed by maintaining clamp        force applied to exceed the the second spring force until a        maximum cross section is below a glass-transition temperature        characteristic of the thermoplastic;    -   e.) Ejecting the molded article by releasing clamp force and        opening the moldset along the parting line.

In accordance with the present invention, once the optical-gradethermoplastic has cooled to at least the glass-transition temperature(for polycarbonate, this equals 296° F.) in even the thickest crosssection, then the resulting molded lens should be shape-stable (theplastic molecules will have memory). Since molding productivity isenhanced by faster heat transfer rates between the cooling melt and themold inserts, it may be advantageous to employ highly-conductivecopper-based alloys, with a hard electroplated chrome or nickel face onthe optically-polished partforming surfaces, as materials forconstruction of the mold inserts. Applicants' U.S. Pat. No. 4,793,953(incorporated herein by reference) is one such example, for use inoptical molding. A further improvement in optical molding thermodynamicsis Applicants' U.S. Pat. No. 5,376,317 (incorporated herein byreference) employs such highly-conductive copper-based alloy moldinserts in a molding cycle which starts with mold insert surfacetemperatures above the glass-transition temperature, then after the moldcavity is filled and packed, drops the mold temperature far below thenormal hot (240-295° F.; 120-150° C.) temperatures used for Rxpolycarbonate lens molding.

The first step of demolding and ejection of the paired lens starts withreleasing clamping forces applied by the injection molding machine,thereby decompressing and extending the resilient member comprising thecombined springs described above. See FIG. 1B, righthand split view,showing the molded lens (16) has already been separated off the B sidecore insert (14) optically-polished partforming surface, creating arelease space (17) between the concave lens surface and the convexinsert surface upon which it was formed. This release space (17)substantially corresponds to the compression strokelength (21)dimension, when the moldset spring is extended or uncompressed byreleasing mold clamping forces exerted by the injection molding machineduring the very start of the ejection phase of the cycle. At the sametime, drafted sleeve surface (19) forming the lens edge uses thermalshrinkage of the molded lens to assist separation off the mold cavitybore (sleeve 20) surfaces. Importantly, were zero draft employed in thebore which forms the lens edge, as is common in today's Rx polycarbonatelenses made by prior art methods, these lenses could be so strongly heldonto the B side mold insert (14) by partial vacuum that the lenses arepulled back when the springloaded parting line B side mold plate (28)comes forward (relative to the B side mold insert). Applicants have seensuch examples, where the still-hot gates are bent or, even worse, tornoff, leaving the lens stuck onto the B side insert deep inside the bore.By applying some positive draft to the B side sleeve, a mechanicalinterference is created which prevents this possibility of the lensesbeing pulled back into the bore.

See FIG. 1B. Note that the parting line (C—C cross-sectional plane) isnot yet opened at all, even though the movable platen has traveledrearward (compare the moldset height measured between A clamp plate (25)and B clamp plate (23) vs. the leftland split view which shows thefully-clamped condition). With or without an optional air blowoff, whenthe parting line starts to open up, the molded paired lenses are alreadytransferred off the B side and are being pulled off the optically-polished partforming surfaces of the A side concave inserts (13) sincethe cold sprue (18) and cold runner (15) of the molded paired lenses arestill firmly attached to the ejector mechanism (which is not yetactuated), using conventional mechanical retention (41) (shown ascontrolled-draft-angle on the cold well (40) of the sprue) to “grip” themolded paired lenses (16) onto the B side. (Also, deliberately runningthe coolant temperatures on the B side cooler than those of the A sidecan cause more shrinkage to occur on the B side of the molded lenses,thus reducing retention forces on the A side of the lens.)

See FIG. 1. As the injection molding machine's mold opening continuesafter the maximum forward travel of the springloaded B side mold plate(28) is reached (set by the shoulder bolt (29)), then the parting lineopens up. Once the A & B sides are no longer held together, strippingforces are automatically applied by this mold opening motion which willexceed the partial vacuum that may exist between the convex surface ofthe molded lens and the corresponding concave mold insert surface uponwhich it was formed, since the molded paired lens are still held bymechanical retention forces (41) onto the movable platen B side of themoldset. As long as these B side retention forces exceed the forcewanting to hold the lenses onto the A side inserts without exceeding thecohesive strength of the plastic in the cold runner and gate, pullingthe lenses off the A side will be mechanically positive when the partingline opens up sufficiently during mold opening.

Next, as shown in FIG. 14 the paired molded lenses (16) and connectingcold runner system including mechanical retention (41) are stripped offthe B side by conventional ejector pins (4), which are driven by motionsof the injection-molding machine's hydraulic ejector cylinder (notshown) tied into the moldset ejector plates (24), to which the ejectorpins (4) are mechanically tied in. Stripping the lenses off the B sidewill also be mechanically positive. This step is done only when themoldset is fully opened up along the parting line, and timing of thisejector motion is only initiated after the end-of-arm tooling of atakeout robot is in place to receive the molded paired lenses whilebeing stripped off of the mechanical retention. This timing iscoordinated between a programmable control of the injection moldingmachine and of the takeout robot, with part verification to confirm thatthis handoff has been made. Many brands and types of takeout robotsexist for plastic injection molding machines. A side entry type ispreferred over the more common “up and out” rectilinear type, since thespace above the mold platens is preferably where downward-facing HEPAfilters will be located, and since a cleanroom enclosure will be smallerand more compact if a side entry type is used. Typical makers of sideentry takeout robots include Ranger Automation of Shrewsbury, Mass.,Conair Martin of Agawam, Mass., and Automated Assemblies of Clinton,Mass.

Note that the above-mentioned ejection sequence differs from theconventional way plastic parts are ejected from injection molding, whichstarts by stripping the molded part off the partforming cavity surfacefirst, when the mold starts to open, while holding the molded part ontothe partforming core surface. After the mold is fully open, either arobot arm or human operator then reaches in and pulls the molded partoff the partforming core surface.

In an optional but preferred embodiment of the present invention,filtered compressed air is employed in accordance with a prescribed “airblow” sequence of steps in order to provide a supplementary drivingforce for separating the molded lens off the optically polishedpart-forming surfaces, to which they are held by natural vacuum due tothermal shrinkage while the mold is closed and the clamping force ismaximized. Although use of compressed-air blowoff to assist ejection isnot new to those skilled in the art of injection-molded thermoplasticsgenerally, Applicants are not aware of it ever being employed in opticallens injection molding, and it is not found in any of the prior-artpatents relevant to this field. Refer to FIG. 1B. Applicants employfiltered compressed air (for cleanliness of part-forming mold surfacesas well as molded lens surfaces), introduced by A side air line (10) andB side air line (11), into the clearance gap (12) formed between theouter perimeter of each cavity insert (A side cavity insert (13) and Bside core insert (14)) aid the bore of circumferentially-surroundingsleeve (20). Air valves (not shown) control the air flow and pressurewithin air lines (10) and (11) to provide air blow in an ejectionsequence, working in combination with conventional ejector pins (4),which are driven by motions of the injection-molding machine's hydraulicejector cylinder (not shown) tied into the moldset ejector plates (24),to which the ejector pins (4) are mechanically tied in.

In an optional but preferred embodiment of the present invention, evenbefore the parting line is opened, filtered compressed air feeds throughthese “vent gap”—sized passageways gap (12) (for polycarbonate lens, agap of 0.001″ (0.025 mm) still will not “flash”), so that the forces ofthe air begin to be applied on the movable platen B side (core side)around the perimeter of the convex insert, and work inward toward thecenter of the lens, to provide a clean separation off the convexpart-forming surfaces of the B side insert. At the same time, draftedsurface (19) of the lens edge uses thermal shrinkage of the molded lensto assist separation off the mold cavity bore (sleeve 20) surface. Toassist separation of the paired lenses off the stationary platen (Aside) of the mold before the parting line is opened, in an optional butpreferred embodiment of the present invention, a second stage of airblowoff can be initiated, wherein similarly filtered air enters uparound the perimeter of the concave optically-polished A side moldinsert perimeter and driving toward each lens center to break thepartial vacuum formed during molding. During this time, a substantialseal is still held by a tiny edge seal overlap (42) of the lens frontonto the lens mold cavity perimeter. See FIG. 1B. If this tiny sealoverlap (42) is missing, air blowoff forces will be substantiallyweakened and may be ineffective, since the air will follow the path ofleast resistance and bypass the lens center, leaving some partial vacuumforce wanting to hold the molded lens in place during the next stage ofejection, which is mechanical stripping the lens off the concave insertsurfaces by the molding machine's clamp-opening stroke while the pairedlenses are being firmly held onto the ejector apparatus which movesalong with the B side of the moldset.

B. For Cleanliness, Never Cut Solidified Plastic Before Dipcoating

Each polycarbonate dipcoated lens is inherently edge-gated and ishardcoated by a glossy film which is easily seen to form a “dripmark”(resulting from gravity flow of the liquid dipcoating onto both frontand back surfaces). To examine such an Rx lens, let us look at a planview of the molded hardcoated lens, and find the location of thedripmark (easily observed as a buildup (37) of the relatively-thickerhardcoating glossy film, as seen in FIG. 2B. When laid out as a clockface, let us arbitrarily designate the location of any lens' dripmark asin the 6 o'clock position. By examining this lens-edge sidewall,starting at the dripmark and going circumferentially all the way around,one can see if any ejector, tabs were used, and if so, were the cutbefore or after dipcoating, because if these tabs would be cut offbefore or dipcoating, it will show a glossy covering over the cutmark/residue, in addition to the degating residue where the gate hasbeen removed.

Observing lenses sampled from the current market, the Gentex and Neolenslens samples typically show one or more ejector tabs, most commonly 180degrees opposite the gate. The Neolens sample showed four such ejectortabs+the gate, all of which were cut off before the cleaning anddipcoating operations (like Comparative Example FIG. 2.)

The reason why tabs in some lens edge locations cannot be tolerated inthe dipcoating process is that liquid coating on the top half of thelens would run down by gravity from the tip of the ejector tab over thelens edge, and this liquid stream of coating will then flow verticallydown from that perimeter location of the ejector tab along the front orback optical surface of the lens. This “coating flow runs” createsnonuniform lightbending (=aberrated image seen when looking through theaccumulated thicker coating), causing a rejection of the manufacturedlens. If one or more ejector tabs must be cut off the moldedpolycarbonate lens before dipcoating, this not only adds to the variablecost (higher resin used per lens, more labor cost for operator handlingand trimming operations, but it also directly reduces surfacecleanliness of the freshly-molded lens. There is no way to cleanly cutsolidified polycarbonate plastic without inevitably generating fineairborne particulates (“polycarbonate dust”), which immediatelyre-deposits onto the front and back optical surfaces of thepolycarbonate lens, because electrostatic attraction forces will drawand bind them to the high-dielectric-constant polycarbonate surfacelayer. Use of ionizing-air blowers can minimize this electrostaticattractive force, but actual tests of freshly demolded lenses withfieldmeters show 5-30 kilovolts of static charge, which is only veryslowly dissipated (in minutes, not seconds) due to excellent electricalinsulation properties of polycarbonate.

Even when no ejector tabs are cut before coating, if the lens must bedegated so that it can be hung via molded-on hanger tab onto thelensholder rack (see Comparative Example FIG. 2), or if a molded pair ofthe lens must have the cold runner cut so that it can be inserted viamolded-on hanger tab into the lensholder rack (see Comparative ExampleFIG. 2A), then these degating and/or runner-cutting operations will alsogenerate the fine polycarbonate dust as airborne surface contaminants.All apparently also some require manual handling by human operatorbetween molding and dipcoating steps. After trimming and mounting intolensholder racks, these polycarbonate lenses are cleaned to remove anysoluble surface contaminants (such as oil) and insoluble particulatesoils (such as airborne inorganic dusts, but most troublesome, the finepolycarbonate particles generated by the trimming and degating andrunner-cutter operations).

Applicants' U.S. Pat. No. 4,828,769 and U.S. Pat. No. 4,900,242licensees' lenses do not use any ejector tabs, as can be verified byexamination of the lens edge. Nevertheless, if the injected shot (into aplurality of lenses connected by cold-runner melt delivery system) mustbe cut apart in order to be mounted into lensholder racks, then theserunner-cutting operations have the same undesirable effect of generatingpolycarbonate dust. The statistically greatest source of percent yieldloss is the flaw category known as “coating clear specks”, wherein atransparent/translucent particle, of sufficient size and location so asto disturb vision, is encapsulated inside the liquid-appliedhardcoating's glossy film. Obviously, vigorous cleaning and multi-stagedilution factor can make a difference in reducing this economic loss andpercent yield. Nevertheless, even with today's best cleaners, it remainsthe greatest source of scrap lenses.

Refer to FIG. 1A. The molded paired lenses of the present invention willhave no hanger tabs (1) in the upper 90-degree quadrant (6) (between10:30 and 1:30 o'clock), will be gated (4) within right and/or left sidequadrants (5) and (−5) (between 1:30 and 4:30 o'clock for (5) andbetween 7:30 and 10:30 o'clock for (−5), respectively), and if they usean (optional) drip tab (not shown), it will be located in lower quadrant(7) (between 4:30 o'clock and 7:30 o'clock). See also hanger tab stem(3) and open-spring head configurations described more in examplesreferring to FIG. 3.

Now see Comparative Examples on FIGS. 2, 2A, 2B and 2C. In contrast tothe cited prior art, note that no ejector tabs are employed on theApplicants' lens perimeter itself (see FIG. 3), and most specifically,not at any location that would require cutting off before diphardcoating.

The Comparative Example of FIG. 2 shows a simplified 2-cavity lensmolding with cold sprue and runner (32). Note that each lens has amultiplicity of ejector tabs and the gate, each of which must be cut(33) in a separate operation afer demolding before dipcoating, usingmolded-on “T” shaped hanger tab (34). The prior art patent which mostclosely resembles this Comparative Example of FIG. 2 is Weber (U.S. Pat.No. 4,008,031), differing only in that Weber's T shaped hanger tab 20 islocated directly opposite the gate 25, with an ejector tab 16 on eachside of tab 20. Weber needs to cut off the gate feeding into drip tab 23before dipcoating can be done.

Bakalar (U.S. Pat. No. 4,644,854), assignment to Neolens, shows in hisFIGS. 4 & 5 use of ejector pin 15 opposite the gate, with no molded-onhanger tab shown. In actual practice, the Neolens molded lens has aplurality of ejector tabs and ejector pins which need to be cut beforedipcoating, in an array just like the Comparative Example of FIG. 2,thus needing 6 cuts (33) to prepare each lens for dipcoating using a tab(34) of unknown shape at the location pictured in FIG. 3.

Weymouth (U.S. Pat. No. 4,933,119), assignment to Gentex, shows noejector pins or hanger tabs, and does not teach any procedures fordemolding or ejecting the molded lens. One must only assume that a humanoperator is employed to manually remove the molded lens, in which casehigh levels of airborne contamination onto the demolded lenses isinherent. All Gentex Rx lenses show at least 1 cut per lens beforedipcoating (the cut is coated over with glossy film).

See now the Comparative Example of FIG. 2A, which shows a simplified4-cavity lens molding with cold sprue 18′ and runner 35 feeding into 2pairs each of lenses, each having a gate 15′. Even if the closest priorart (Applicants' U.S. Pat. No. 4,878,969 and U.S. Pat. No. 4,900,242)were to be configured into 2 pairs as shown instead of 4 single lens,and even if a molded-on feature for gripping and fixturing were addedonto the runner for each pairs, there is still no way to dipcoat theselenses as they are demolded, without at least 2 cuts (33) to separatethe 4-cavity shot into the 2 pairs.

There are additional limitations Applicants' U.S. Pat. No. 4,878,969 andU.S. Pat. No. 4,900,242. See the ejection sequence in FIGS. 6, 7, and 8,wherein the resilient member 13 is kept in its compressed or retractedposition, so that when ejector plate 17 is pushed forward by theinjection molding machine when the mold parting line is completely open,then the B-side inserts 5b is pushed forward past the parting lineplane, as shown in FIG. 8, and the molded optical lens or disk isejected 97, as shown. This method of Rx lens ejection is NOT desirablefor use with an in-line mold and dipcoat process scheme of the presentinvention, however. This reciprocating back-and-forth B side insert'smotion within a tightly-fitting bore of at least several millimeters(high-minus, finished-single-vision lenses can easily be 10 mm edgethickness) must inevitably cause metal-to-metal wear and resultinggalling (seen as scoring lines when viewing the molded lens edge thus isconfirmed by visual examination of the molded lens edge of Applicants'licensee which uses this “traveling insert” method of ejection). Themetal-to-metal wear that results must generate tiny metal particulatecontamination which can be deposited on both the molded lenses and thepart-forming surfaces of this optical mold, thus creating cosmeticrejects in the dipcoated lenses. Secondly, if severe galling takesplace, the resulting irregular surface profile of the bore which formsthe mold cavity sidewall then permits molten plastic to flow into thesetiny galled-in crevices, which then gets sheared off during ejectionforces (as the traveling insert is pushed forward), thus creating a fineparticulate plastic “dust” for further airborne contamination of thedemolded lenses and molding surfaces. For these reasons, thetraveling-insert method is formed not to be acceptable for the in-line,automated molding and dipcoating of the present invention.

Referring again to Applicants' U.S. Pat. No. 4,878,969 and U.S. Pat. No.4,900,242, note that FIG. 9B shows drip tabs 99 in the 6:00 o'clockposition of the molded lenses, but that even if there was a way ofseparating the two molded pairs shown without cutting aftersolidification of the plastic, the small cold well 31 is not locatedhigh enough to clear the lens edge so as to serve as a gripper or hangertab for dipcoating, nor can cold-runner firm sprue 19 be separatedwithout a cutting operation, which would generate plastic dustcontaminants.

Refer now to FIG. 2C Comparative Example, showing a typical prior artsingle lens with tab (34) at 12:0 o'clock position. If dipcoatingimmersion strokelength is not extremely accurate, and the lens isimmersed not just to the top lens edge but further, partway up the stemof the tab, then the liquid will run back down by gravity this stem,thus causing flow runs (38) streaming back onto the lens' optical faces.This is minimized but not entirely eliminated by reducing the tabthickness and setting tab (34) back some distance from either face.Weber (U.S. Pat. No. 4,008,031) is one such example.

Refer now to FIG. 2D Comparative Example, showing a Liebler (GB 2 159441A) prior art single lens with a tab (34) of the full thickness of thelens, at 12:00 o'clock position. Refer also to Liebler's FIG. 2, fromwhich this lens is taken, showing lens F with lug 10 and driptab 11. Ifdipcoating immersion strokelength is not extremely accurate (which isimpossible with Liebler's “endless conveyor” dipping the lens), the lenswill inevitably be immersed partway up the stem of the tab, then theliquid will run back down by gravity this stem, thus causing a largeflow runs (38) streaming back onto the lens' optical faces.

C. Lens Edge Detail Design for Clean Ejection

Refer back to Applicants' FIG. 1, which shows a drafted surface (19) ofthe mold cavity bore which forms the lens edge sidewall detail. In anoptional but preferred embodiment of the present invention, thissurface's draft angle will be a positive value, when compared tovertical (“zero draft”). This draft angle generally should be increasedin value directly proportionally as lens edge thickness is increased.Also, note that adding a slight molded-on rim at the junction of theconvex surface and lens edge sidewall (typically, no more than 0.5 mmper side is sufficient) which acts as a edge seal (42) (see FIG. 1B)facilitates compressed-air blowoff which is optional but preferred withthe present invention.

Molded or cast Rx lens blanks are sold in nominal diameters, rounded offto integral millimeters. Since all cast or molded plastic spectacle lensblanks are subsequently cut down on their perimeters so as to fit insidea specific spectacle frame of the patient's or prescribing doctor'schoice, inherently all Rx lenses will be “laid out” to fit the matingspectacle frame. Because of various blemishes and flaws which canaccumulate at the edge of cast Rx lens (such as bubbles or voids) andmolded plastic lens (such as residual knit line or gate blush) or, dueto the dip hardcoating (such as “dripmark”), the rule of thumb is toprovide a waste zone, consisting of a perimeter band of 5 mm widecircumferentially around the lens edge. Thus, on a 76mm-nominal-diameter lens blank, for layout purposes, only the inner 66mm would be considered usable, when subtracting 5 mm waste zone perside.

The present invention utilizes the fact that waste zone exists in orderto alter lens product edge and sidewall details for improvedmanufacturability. Refer again to FIGS. 1, 1A and 1B. Most specifically,in an optional but preferred embodiment of the present invention,Applicants provide for a plurality of interchangeable sleeves (20), eachof which which can be selected with its different drafted surfaces (19)and assembled together with the appropriate mating convex insert (14) inorder to mold each different lens power, so as to provide the cleanestpossible release of the molded paired lenses free of solid metal orplastic particulates being generated by the ejection process. No onesuch sleeve draft angle or surface geometry can be optimum for all RxFSV lens molding, which must encompass a wide range of productgeometries. If too steep a draft angle is used all the way down the boreand sleeve surface which forms the lens sidewall, there will be a largeenough clearance gap formed between the sleeve and the insert to“flash”, which is unacceptable. Specifically, to mold a complete matrixof FSV plus- and minus-powered lenses will require the mold design toaccommodate widely differing lens edge thickness. Plus-poweredmagnifying lenses (for correcting farsightedness) will have typically, aminimal lens edge thickness (2.0-0.8 mm). Conversely, demagnifyingminus-powered lenses (for correction of myopia and nearsightedness),will have comparatively much thicker lens edge thicknesses (2.0-12.0mm). Having zero draft angle on the thickest lens edges would becomeproblematical. Nevertheless, because the mold tooling becomes much morecomplicated, the prior art patents show no such provision for changeableor adjustable draft angles. In actual practice, measuring somecommercially available Rx lenses believed to be made by the citedprior-art patents shows a zero draft angle and, therefore, reliance upon“brute force” to mechanically push out the lens in spite of highretention forces therein. Doing this also increases the probability ofgenerating both metal-to-metal wear and shearing of metal to plastic,both of which produce solid particulate surface contaminations.

As shown in FIGS. 1A and 1B, the present invention employsinterchangeable mold sleeves (20) which become the part-forming surfacesfor the lens' sidewall edge. By interchanging one set of such sleeveshaving a certain pre-determined drafted surface (19) with another sethaving a different pre-determined drafted surface/ angle so as to Niatewith the corresponding B-side inserts for a specific desired FSV-powerminus lens, one can controllably increase or decrease the draft angle ofthe resulting molded paired lenses for the full range of FSV lenses asthey are ejected, for cleanest molded-lens quality. The thicker the lensedge, and correspondingly higher minus power, the greater the draftangle that should be applied, but preferably only part way down thesleeve. For example, a −2.00 Diopter lens may have an edge thickness of4.2 mm, and it will release cleanly with a drafted edge of only 1.9 mm.Conversely, a −5.00 Diopter FSV lens having a nominal edge thickness of14.6 mm has clean release by using an increased drafted edge of 7.2 mm.

D. Molded-On Tab Designs Suited For Robotic Manipulation in DipcoatingProcess Steps

After paired lens, having the above-mentioned elements of the presentinvention, are formed within multicavity injection-compression molds ofthe present invention and are solidified therein, demolding is donewithin a cleanroom enclosure maintained preferably at a positivepressure (vs. ambient) from HEPA blower units. A take-out robot isneeded; preferably, the side-entry type, not “up and out” type, so thatmodular blowers supplying HEPA-filtered air can be located directlyabove the platens onto the molding machine, to maintain a preferablypositive-air-pressure within the clean room enclosure whichsubstantially surrounds the mold (a deliberate gap located under themold for an air exhaust may, improve the downward-directed laminar flowpattern; similarly, a bottom gap for directed air exhaust is preferablylocated below the dipcoating machinery).

This side-entry takeout robot operates within a cleanroom-enclosedtunnel between the enclosed mold and an enclosed HEPA-filtered automateddipcoating machine. When the mold is opened at the parting line and theside-entry takeout robot's arm is moved into position, each pair of lensare ejected forward into gripping jaws of end-of-arm tooling mounted onthe side-entry takeout robot's arm. In an optional but preferredembodiment, this robotic dipcoating machine with its self-contained,cleanroom-filtered air, positive-pressure HEPA filter will be locatedbetween two such injection molding machines and multi-cavity molds, withtwo such side-entry robots feeding paired lenses into this one roboticdipcoating machine. This “duo line”, in-line system may be economicallypreferred embodiment versus a single molding machine and mold fed to asingle coating machine, since typically Rx-lens molding cycles arerelatively long (1-5 minutes, depending upon Rx lens power andcorresponding molding thickness). With longer-cycling lenses, the duoline configuration de-bottlenecks the molding step, for increasedcapacity output per unit of capital equipment cost.

See FIG. 4B, showing a block diagram flowsheet of the presentinvention's steps, within a single cleanroom enclosure (designated bythe dashed-line, showing all steps are performed within its cleanroomairspace perimeter).

This robotic device or dipcoating machine may take a number ofconventional forms with automated transport driven by chain-driveconveyors (operating singly or in parallel, connected by crossbarswhereon the lensholder racks would be hung), or, alternatively, anindexable overhead conveyor or walking-beam conveyor. An optional butpreferred embodiment employs a programmable SCARA cylindrical-type robotof the kind manufactured by IBM, GMF Fanuc, and Seiko. Such a SCARArobot should have a suitably-large (typically, up to 270 degreesrotation and at least 100 mm Z axis ) work envelope, so as to be able totransfer these molded paired Rx lenses from a hand-off point somewhereinside the coating-machine clean-room enclosure to at least onehardcoating diptank, wherein a computer-programmable sequence ofimmersion times and withdrawal speeds can be employed, followed bytransfer to a holding device which is part of a curing workstationfitted with conveying means therein.

See FIG. 3, showing the paired molded lenses with hanger tab (1)comprising stem (3) and head (4), as they are received from theside-entry takeout robot directly or indirectly handed off to the secondrobotic device. Note dashed line (39) showing the liquid level of thedipbath—everything below that line (39) will be immersed in thehardcoating solution. Note the workholder-mating horseshoe-shaped head'scontoured surfaces (50 lead angle taper), (52 detent), and (53 insertionlead angle) are preferrably located above the liquid level (39), so asto not contaminate downstream area where mechanical mating mightdislodge coating flakes.

See now FIG. 3D. Preferably, this receiving second robotic device willbe a programmable SCARA cylindrical-type robot arm fitted with a rotarywrist (not shown) capable of rotationally moving (70) about axis (69),and paired gripping jaws ((43) left and (60) right) which can movetogether (68) to grip or ungrip, in accordance with the program. See nowFIG. 3C. Although the jaws are cut as substantially mirror-images of thehead surface contours (50 lead angle taper), (52 detent), and (53insertion lead angle), there is additional clearances ((63) vertical and(62) horizontal) provided for imprecise robotic “handoffs” whentransferring the paired molded lenses from one workstation or operationstep to another. Such clearances provide tolerance for slightmisalignments or positional errors, yet complete the pickup or handoffproperly.

The gripping orientation shown in FIG. 3C is how the SCARA robot wouldhold the paired molded lenses during the dipcoating step's lowering andraising operations, after which the wet lenses can then be placed intoone of the multiple workholder arms having a substantially-matedmirror-image-machined “nest” of FIG. 3B having tapered angle (50′), andstem placement relief (57) and stem retention step (58), with stemclearance (56). Such a workholder will be then used to automaticallytransport the wet lens through drying and curing steps. Means for suchautomatically transport can be conventional conveyors, but in anoptional but preferred embodiment, a rotary index drive is fitted withmany such workholder arms, as a carousel within the curing workstation.

The gripping orientation shown in FIG. 3D is how the SCARA robot wouldhold the paired molded lenses during the insertion of the head into alensholder rack or similar fixture, wherein the receiving nest (notshown) has a protruding surface for mechanical interference with headdetent surface (52) to prevent the head from being easily dislodgedduring transport. Insertion then requires the robot to exert a pushingforce in the axial direction of the stem toward the head, sufficient todeflect the spring—the lead angle surfaces (53) assist in this frictionfit, as does the spring relief (51) (the greater the relief and thethinner the legs, the easier to deflect the horseshoe shaped spring).Removal is the reverse of the insertion. Typically, this insertion willbe done after the paired dipcoated lenses have been cured (at least to atackfree state), then inserted into a rack holding many pairs, fortransport manually after leaving by the cleanroom to such otherdownstream “batch” operations as inspections (by humans), degating andpackaging.

Another optional, but preferred, embodiment uses an intermediate step ofrobotically placing the molded paired Rx lens into a circulatingfiltered alcohol tank for a prescribed residence time therein, toperform the following functions:

-   -   1. De-statisizing (measuring surface charge by field meter,        before immersion, the lens has at least 4-10 electron volts'        static charge, even after being held under ionizing blower for a        prescribed period of time; after alcohol-bath immersion of at        least a couple of minutes, the lens has virtually no measurable        surface charge).    -   2. Thermal cooling-off (measured immediately after demolding        with a noncontact infrared pyrometer, the polycarbonate Rx lens        typically shows a temperature of as high as 250° F. (125° C.) or        higher; depending on residence time and alcohol bath        temperature, this can be reduced to 120-60° F., as may be        required, depending upon solvent composition in the liquid        hardcoating bath, to prevent “solvent burn” of the molded        polycarbonate lens surfaces. It is well-known to those skilled        in the art that certain solvents found in today's state of art        hardcoating bath compositions can excessively attack a warm        polycarbonate lens, causing cosmetic rejectable flaws due to        excessive etching, frosting, and solvent-burn phenomenon, while        being tolerant of the same lens at lower temperature.    -   3. Low-kinetic-energy cleaning/rinsing (soluble organic surface        residues and lightly-held insoluble particulates can be removed        by the circulating alcohol)

Advantages for using such an alcohol bath are evident especially if thehardcoating is solvent-based, since such solvents will typically attacka freshly-demolded hot (measured by noncontact infrared, actual temp canbe 250° F. (125° C.) or higher) polycarbonate lens surface to create anetch or partly-dissolved surface layer—both damaged surfaces areoptically rejected flaws. At room temperatures, the same dipbathsolvents may not harm the lens. The problem then is that cooling in airtakes many minutes, during which time even the best destaticizedpolycarbonate lens still has high enough surface charge (typically>3 KV)to attract any airborne dusts which are further stirred up by thelocalized thermal air currents created by the hot lenses, so even in aHEPA cleanroom, the hot clean lenses gradually become cool less-cleanlenses. By immersing the hot paired lenses as soon as possible into thealcohol bath, they stay pristinely clean while heat is removed muchfaster (reducing the number of pairs of lenses held in the cooling stagebefore dipcoating, so the equipment can become more compact), andsurface charge becomes zero. For this immersion time of several minutesduration, it is best to have the robot place the paired lenses into analcohol tank fitted with a stainless steel cover (or inert plasticequivalent) into which has been machined as many multiple head-mating“nests” (as shown in FIG. 3B) as are needed—the longer the immersiontime desired, the more the number of nests and the larger the tank mustbecome.

If such an alcohol bath is utilized before dipcoating, it is possible towait too long—long enough after removal from the alcohol bath to let themolded, paired lens dry completely before immersing it in the liquidhardcoating dipbath. To do so permits airborne particles to deposit ontothe cleaned dry lens surfaces, even briefly before entering into theliquid dipbath. Therefore, an optional, but preferred, embodiment foruse of the alcohol bath would not allow complete evaporation of thealcohol wet film off the molded paired Rx lens before immersion into theliquid hardcoating dipbath. Instead, wet alcohol films should remain onthe lens when immersed into the dipbath, where the lenses are kept for asufficiently-long residence time so as to remove any remaining wet-filmof alcohol (and any airborne particles which may have become entrainedtherein during the transfer time from alcohol bath to dipcoating bath).Displacing wet-films of alcohol on the lenses' surface with the liquidhardcoating bath is achieved by a combination of high rate of internalcirculation of the liquid hardcoating, as well as some programmed-inmechanical motion by the robotic arm holding the lenses to provideagitation and turbulence.

This SCARA-dipping and alcohol-bath approach assumes that the liquidhardcoating bath composition contains at least one or more alcohols insome significant percentage, and that gradual increase during operationswithin a certain % range of alcohol by dragout of the wet film onto themolded lens will not disrupt desired solvent balance and drydowncharacteristics of the liquid hardcoating dipbath. Such liquidsolvent-based hardcoating compositions ideally suited for this protocoland for use with the SCARA robot will also be of low-to-moderateviscosity (preferably, <10 centistoke; most preferably, <5 cs.), so asto give efficient mixing/removal of the wet alcohol film off the lenswithin the dipbath without entraining air bubbles, and to easily flowout smoothly after any vibrations from the SCARA dipping motions.Another way to get smooth coatings from such unconventionally thinviscosity (2-10 cs.) dipbaths is to employ unconventionally fastwithdrawal speeds (at least 20 inches per minute, preferably 0.5-5inches per second, most preferably 1-3 inches per second; conventionaldipbaths of >10 cs. use 2-12 inches per minute), and to follow the firstdip with at least a second dip. In such a preferred fast withdrawalspeed double-dip process, the dipbath should be relatively fast-drying(by choosing selected high-evaporation-rate solvents such as lowmolecular weight alcohols and ketones), so as to give smooth coatingsfree of coating flow runs or “sags”, while using relatively dilute(typically <25% solids) dipbath with a moderate-to-low hardcoatingpolymer molecular weight.

Depending upon the chosen liquid hardcoating crosslinking chemistry, thecuring workstation will be configured so as to provide the desired cureprotocol. For example, a simplest version would be a solvent-freeUV-curable hardcoating, in which case the curing workstation mightsimply consist of a battery of UV lamps of the electrodeless type (madeby Fusion Systems of Rockville, Md.) or conventional mercury-arc UVlamps, with the lenses having been robotically placed onto carriers ofsuspended from an overhead conveyor, so as to present the paired, moldedlenses' front and back surfaces to line-of-sight exposure to these UVlamps for a sufficiently-long time to effect desired cure. However,doing so may preclude use of the alcohol bath. Another variant of such aconfiguration would be solvent-based UV cure, in which case a solventdrydown stage would precede the UV-cure-lamp stage (infrared lampsrepresent an energy-efficient way of devolatilizing such coatings,provided again that the molded, paired Rx lens are presented inline-of-sight orientation to this bank of infrared lamps), to dry bothfront and back lens surfaces. Then the principles of the above paragraphmay apply.

All commercially-desirable heat-curing liquid hardcoats aresolvent-based, so inherently a solvent-evaporation/coating-drydown stagemust be employed before accelerated heat cure is given. As previouslymentioned, if the lens orientation permits line-of-sight exposure to abank of infrared lamps, doing so is an energy-efficient way of achievingthis end. Once fully devolatilized, additional exposure to infrared canprovide full crosslinking, or, optionally, a lesser dosage can providegelation to a sufficiently hard film so as to be “tackfree” (meaningairborne dusts will not permanently stick to such surfaces, so tackfree,hardcoated lenses can safely be handled manually outside the clean-roomenclosure without resulting in yield loss due to coating clear specks.Optionally, a tackfree state might be desired in order to re-cycleflawed coated lenses—any inspected lenses which have coating flaws canbe easily recycled by immersion into a suitable solvent to strip thetrackfree, gelled coating which is not yet fully crosslinked, thusremoving the flawed coating film and allowing the paired molded lensesto again be fed through the cleaning and dipcoating protocol.

An optional but preferred embodiment of a curing workstation may employa rotary indexing table fitted with multiple arms, having eithergrasping jaws, suction cups or sculptured mechanical nests, adapted forreceiving the molded paired Rx lenses that have molded-on hanger tabs.An especially preferred embodiment employs the SCARA robot to preciselyplace the head of the hanger tab into a substantially mechanicallymating geometry (preferably with a tapered lead-angle fit) nest of thetype shown in FIG. 3B, and located near the end of each of these arms.

A further optional but preferred embodiment of this special type ofcuring workstation would then allow for a settable rotation of the arm,such that the position of the molded, paired Rx lens can be varied froma “straight down” vertical orientation (wherein the molded, pairedlenses hanging vertically direct down from the arm, at a 90-degreeangle), and by rotation of the arm, this angle can be successivelyreduced to some minimal angle of perhaps 10 degrees or so below thehorizontal orientation. (See FIG. 3B, retention step (58)) Thisoptional, but preferred, embodiment has the advantage of employinggravity to create a more uniform coating flowout pattern distributed allacross the lens surface. This is believed to be especially important forthose Rx lenses having strong plus powers (steep, convex front curvedsurfaces), and also multi-focal lenses having a ledged bifocal ortrifocal segment (“D seg”). Those two types of lenses are particularlyproblematical when the coating is dried and cured in a substantiallyvertical orientation due to gravity then increasing the nonuniformity offlowout of the liquid hardcoating. Refer to Weber (U.S. Pat. No.4,443,159) coating patent.

E. Process Flowsheets for Add-On Steps in Continuous-Process, following“Mold and Dipcoat”

In yet another optional but preferred embodiment, after the molded andhardcoated lenses are cured at least to a tackfree state, the lenses arethen robotically transferred into an adjoining extension of the samecleanroom enclosure which contains an automated computer-assisted-visionlens inspection system, for cosmetic inspection. See FIG. 4C. Suchautomated lens inspection machines typically use pattern recognitioncomputer software with a video and/or laser-scanning noncontactinspection, and make comparison of the resulting image against thecomputer's decision rules for “go” and “no-go” acceptance of anycosmetic flaw deviations. However, such an optical computerizedinspection system for cosmetics relies upon high-resolution imagery anda large proportion of all cosmetic rejects are at the surface of thehardcoated lenses (“coating clear specks” and “coating flowout runs”,especially). One such manufacturer of Rx FSV lens automated inspectionmachines is Non-Contact International, of Maumee. Ohio.

Such inspection system in giving desired results (i.e., rejecting badlenses and accepting good lenses) must not reject “good” lenses whichonly have a lightly-held dust particle laying loosely on the lenssurface. Cleanliness of the lenses coming into the inspection system isthe biggest problem in its use so far. Elaborate and costly multi-stagecleaning equipment workstations and protocols have been necessitated toproperly use such equipment. A particularly advantageous combination ofthe present invention with such machines would employ this matedcleanroom (so the lens never leaves the Class 100 clean air environment)operating with positive pressure without any human operator within thatairspace, so that paired tackfree-hardcoated lens are kept in a pristinestate as they leave the curing workstation directly to the videoinspection station. Cosmetic rejects caught at this tackfree state canthen be robotically set aside and recycled through solvent stripping,re-cleaning, and re-dipcoating, as mentioned earlier.

See flowsheet of FIG. 4D. Yet another optional but preferred embodimentof the present invention takes the hardcoated lens to full crosslinkedstate before leaving the curing workstation, then robotically transfersthe molded fully-cured hardcoated paired Rx lens within an adjoiningextension of this mated clean-room enclosure maintained under positivepressure (HEPA-filtered air of typically Class 100 purity), wherein thisconnected-clean-room enclosure contains a thin-film anti-reflective(“AR”) vacuum-coating machine fitted with multiple load locks andproduct workholders adapted to the molded, hardcoated, paired lenses.FIG. 4D shows a block diagram flowsheet of the present invention'ssteps, within a single cleanroom enclosure (designated by thedashed-line, showing all steps are performed within its cleanroomairspace perimeter). This continuous-process anti-reflective vacuumcoating system would typically contain the following steps:

-   -   1. After the load station, pull at least a rough vacuum before        transferring to a second vacuum stage via load lock, wherein a        final vacuum is pulled.    -   2. At that point, some surface preparation protocol, such as        ionizing plasma or electron gun discharge, can be used to clean        and/or modify surface chemistry of the top few molecular layers        of the hardcoated Rx lens, either in this chamber or in the next        chamber connected by load lock.    -   3. Once such surface preparation is completed, robotic transfer        via load lock moves the paired lens into the vacuum-deposition        chamber, wherein an AR film is deposited. Preferably, a        high-arrival-energy type AR film is deposited by sputtering or        by ion-gun-assist, so as to provide a desirably-dense-and        strongly-adherent coating AR film onto one or both optical        surfaces of the hardcoated paired lens.

Such a continuous-process automated-transfer AR-coating machine would bedirectly analogous to similar machines used by the hundreds forcontinuous-process aluminum-sputter-coating onto injection-moldedpolycarbonate compact discs. Leading vacuum-coating equipmentmanufacturers as Leybold, Balzers, and Denton Vacuum have provided suchmachines for integrated-molding-and-coating of compact discs (CDs).

1. As an An article of manufacture, thermoplastic injection-moldedpaired spectacle lenses formed within a moldset having a parting linefor opening between an A side and a B side of said moldset, said pairedlenses being suited as a unit of transfer in a multi-step automatedmanufacturing process comprising at least an automated demolding step,an automated liquid dip hardcoating step, and an automated drying andcuring step, said process being performed robotically within a cleanroomair enclosure, wherein said paired lenses are robotically handled fromsaid demolding step through said dip hardcoating step and until said diphardcoating has been dried and cured at least to a tackfree state withinsaid cleanroom air enclosure, said paired lenses comprising the elementsof : (a) two thermoplastic injection molded spectacle lens joined into apair, each of said lens having an outer perimeter forming a lens edgecontoured for release out of a lens mold cavity, said outer perimetercomprising four 90-degree quadrants defined in accordance with a clockface, wherein an upper 90-degree quadrant is defined as being between10:30 and 1:30 o'clock locations on the lens perimeter, a lower90-degree quadrant is defined as being between 4:30 and 7:30 o'clocklocations on the lens perimeter, a righthand side 90-degree quadrant isdefined as being between 1:30 and 4:30 o'clock locations on the lensperimeter, a lefthand side 90-degree quadrant is defined as beingbetween 7:30 and 10:30 o'clock locations on the lens perimeter, (b) acold runner having a sprue connecting therebetween a left lens and aright lens in each pair, said cold runner being formed after moltenthermoplastic flow from said sprue in fluid communication with said leftlens and said right lens is stopped and then cooling to solidificationand joins together the lenses into a pair when cooled, said cold runnerbeing located in the righthand 1:30-4:30 o'clock side quadrant of theleft lens and said cold runner being located in the lefthand 7:30-10:30o'clock side quadrant of the right lens between said right lens and leftlens, (c) an integrally-molded hanger tab located substantiallyequidistant between said right lens and said left lens of said pairedlens, said hanger tab having a stem rising substantially vertically outof said cold-runner connecting said paired lenses, said hanger tabhaving a head located on said stem at a point above a highest lens edgewhen said paired lenses are held vertically in a dipping position, so asto prevent liquid dip hardcoating from contacting robotic means forgripping said head, and said paired lenses formed within said moldset atthe end of each molding cycle are robotically handled in the followingprocess steps: (i) ejecting cleanly off said B side of said moldsetbeing opened along the parting line, said step of ejecting beinginitiated only when end-of-arm tooling of a takeout robot is in place toreceive said paired lenses; (ii) handling said paired lenses byautomation within said cleanroom air enclosure without any humanoperators therein, without any cold runner cutting step or any step oftrimming of any tabs off the molded lens before dipcoating, and withoutuse of Freon CFC nor aqueous cleaning protocols before dipcoating; (iii)dipcoating said paired lenses by said robotic means gripping said headwhile preventing liquid dip hardcoating from contacting said roboticmeans; (iv) drying and curing after dipcoating said paired lenses atleast to a tackfree state within said cleanroom air enclosure .
 2. Anarticle of claim 1 wherein said paired lenses are formed withinmulticavity injection-compression molds employing a variable volume moldcavity process.
 3. An article of claim 1 wherein each of said lenshaving an outer perimeter forming a lens edge contoured for release outof a lens mold cavity, and said lens edge has a positive draft angleformed on said B one side.
 4. An article of claim 1 wherein said coldrunner having a sprue connecting therebetween a left lens and a rightlens in each pair, and said sprue has a cold well having negativecontrolled-draft-angle to grip said paired lenses onto said B one side.5. An article of claim 1 wherein each of said lens having an outerperimeter forming a lens edge contoured for release out of a lens moldcavity, and said lens edge has an edge seal overlap on said A one side.6. An article of claim 1 having an additional element of (d) one or moreejector tabs are being employed, said ejector tabs only being locatedalong the lens perimeter so as not to interfere with proper dipcoatingand not to propagate coating flowout runs, and none of such tabs beinglocated in the upper quadrant.
 7. An article of claim 1 having anadditional element of (d) one or more drip tabs are being employed, saiddrip tabs only being located along the lens perimeter in the a bottomquadrant of each lens (4:30-7:30 o'clock positions) , to minimizedipcoating dripmark size, by capillary wicking action to drain offexcess liquid coating once the molded paired lens have been fullyremoved from immersion in the a dipbath.
 8. An article of claim 1wherein said paired lenses are polycarbonate spectacle lenses for visioncorrection.
 9. An article of claim 1 wherein said a takeout robot is inplace to receive said paired lenses upon ejection is of a side entrytype, and modular blowers supplying HEPA-filtered air are locateddirectly above platens of an injection molding machine within which saida moldset is mounted, so as to maintain a positive-air-pressure withinsaid a cleanroom air enclosure which substantially surrounds saidmoldset.
 10. An article of claim 9 wherein said side entry type takeoutrobot operates within a clean-room-enclosed tunnel between said moldsetand an enclosed HEPA-filtered automated dipcoating machine.
 11. Anarticle of claim 1 wherein after said a takeout robot has received saidpaired lenses upon ejection from a moldset, a step of cooling andremoval of electrostatic charge of said paired lenses is performedbefore said step (iii) of dipcoating.
 12. An article of claim 1 11wherein said step of cooling and removal of electrostatic charge of saidpaired lenses is performed by immersion into a circulating filteredalcohol bath before said step (iii) of dipcoating.
 13. An article ofclaim 1 wherein said step (iii) of dipcoating said paired lenses employsa programmable SCARA cylindrical type robot, as a second robotic deviceto grip said paired lenses by said hanger tab, said programmable SCARAcylindrical type robot being fitted with jaws cut with a mating geometryfor retaining said head of said hanger tab of said paired lenses, forgripping said head while preventing liquid dip hardcoating fromcontacting said robotic means robot.
 14. An article of claim 13 whereinsaid step (iii) of dipcoating said paired lenses employing saidprogrammable SCARA cylindrical type robot gripping said paired lenses bysaid hanger tab employs: (a) a filtered circulating bath of liquidhardcoating of 2-10 centistoke viscosity; (b) a withdrawal speed of atleast 20 inches per minute.
 15. An article of claim 14 wherein said step(iii) of dipcoating said paired lenses employing said programmable SCARAcylindrical type robot gripping said paired lenses by said hanger tabfurther employs: (a) a filtered circulating bath of liquid hardcoatingof 2-5 centistoke viscosity and formulated at less than 25% solids usingmainly high-evaporation-rate solvents such as low molecular weightalcohols and ketones; (b) a withdrawal speed of 0.5-5 inches per second;(c) following a first dip with a second dip.
 16. An article of claim 1wherein said step (iv) of further comprising drying and curing afterdipcoating said paired lenses at least to a tackfree state within said acleanroom air enclosure which employs a rotary index drive fitted with aplurality of workholder arms, each workholder arm being fitted withmating geometry for retaining said head of said hanger tab of saidpaired lenses, operating as a carousel curing workstation .
 17. Anarticle of claim 1 wherein said a further comprising the step ofinserting said paired lenses into a lensholder rack within said acleanroom air enclosure which employs said head of said hanger tab ofsaid paired lenses for a spring interference fit for its mechanicalretention means.
 18. As an article of manufacture, polycarbonateinjection-compression molded paired spectacle lenses for visioncorrection formed within a variable volume multicavity moldset having aparting line for opening between an A side and a B side of said moldset,said paired lenses being suited as a unit of transfer in a multi-stepautomated manufacturing process comprising at least an automateddemolding step, an automated liquid dip hardcoating step, and anautomated drying and curing step, said process being performedrobotically within a cleanroom air enclosure, wherein said paired lensesare robotically handled from said demolding step through said diphardcoating step and until said dip hardcoating has been dried and curedat least to a tackfree state within said cleanroom air enclosure, saidpaired lenses comprising the elements of: (a) two polycarbonateinjection-compression molded paired spectacle lens for vision correctionjoined into a pair, each of said lens having an outer perimeter forminga lens edge contoured for release out of a lens mold cavity, and saidlens edge has a positive draft angle formed on said B side, said outerperimeter comprising four 90-degree quadrants defined in accordance witha clock face, wherein an upper 90-degree quadrant is defined as beingbetween 10:30 and 1:30 o'clock locations on the lens perimeter, a lower90-degree quadrant is defined as being between 4:30 and 7:30 o'clocklocations on the lens perimeter, a righthand side 90-degree quadrant isdefined as being between 1:30 and 4:30 o'clock locations on the lensperimeter, a lefthand side 90-degree quadrant is defined as beingbetween 7:30 and 10:30 o'clock locations on the lens perimeter, (b) acold runner having a sprue connecting therebetween a left lens and aright lens in each pair, said cold runner being formed after moltenthermoplastic flow from said sprue in fluid communication with said leftlens and said right lens is stopped and then cooling to solidificationjoins together the lenses into a pair, and said sprue has a cold wellhaving negative controlled-draft-angle to grip said paired lenses ontosaid B side, said cold runner being located in the righthand 1:30-4:30o'clock side quadrant of the left lens and said cold runner beinglocated in the lefthand 7:30-10:30 o'clock side quadrant of the rightlens, (c) an integrally-molded hanger tab located substantiallyequidistant between said right lens and said left lens of said pairedlens, said hanger tab having a stem rising substantially vertically outof said cold-runner connecting said paired lenses said hanger tab havinga head located on said stem at a point above a highest lens edge whensaid paired lenses are held vertically in a dipping position, so as toprevent liquid dip hardcoating from contacting robotic means forgripping said head, and said paired lenses formed within said moldset atthe end of each molding cycle are robotically handled in the followingprocess steps: (i) ejecting cleanly off said B side of said moldsetbeing opened along the parting line, said step of ejecting beinginitiated only when end-of-arm tooling of a side entry takeout robot isin place to receive said paired lenses; (ii) handling said paired lensesby automation within said cleanroom air enclosure without any humanoperators therein, without any cold runner cutting step or any step oftrimming of any tabs off the molded lens before dipcoating, and withoutuse of Freon CFC nor aqueous cleaning protocols before dipcoating; (iii)cooling and removal of electrostatic charge of said paired lenses; (iv)dipcoating said paired lenses with a programmable SCARA cylindrical typerobot, as a second robotic device to grip said paired lenses by saidhanger tab, said programmable SCARA cylindrical type robot being fittedwith jaws cut with a mating geometry for retaining said head of saidhanger tab of said paired lenses, for gripping said head whilepreventing liquid dip hardcoating from contacting said robotic means,employing: (a) a filtered circulating bath of liquid hardcoating of 2-10centistoke viscosity; (b) a withdrawal speed of at least 20 inches perminute (v) drying and curing after dipcoating said paired lenses atleast to a tackfree state within said cleanroom air enclosure, employinga rotary index drive fitted with a plurality of workholder arms, eachworkholder arm being fitted with mating geometry for retaining said headof said hanger tab of said paired lenses, operating as a carousel curingworkstation.
 19. An article of manufacture comprising: a thermoplasticmolded lens; a cold-runner attached to the lens; the cold-runnerincluding a stem with a free end portion, the free end portion includinga point above a highest lens edge when the lens is held in a dippingposition, the free end portion to provide a first position for a roboticgrip, the stem including a second position along the length for arobotic grip.
 20. The article of manufacture as recited in claim 19,wherein the free end portion includes a forked head to provide the firstposition.
 21. The article of manufacture as recited in claim 20, whereinthe forked head includes detents which are configured to receive therobotic grip to prevent dislodging of the forked head during transport.22. The article of manufacture as recited in claim 21, wherein theforked head includes legs which deflect inwardly to provide a springforce to prevent dislodging of the forked head during transport.
 23. Thearticle of manufacture as recited in claim 19, wherein the stem includesa bulged portion to provide the second position.
 24. The article ofmanufacture as recited in claim 23, wherein the bulged portion extendslaterally outward from the stem.
 25. The article of manufacture asrecited in claim 23, wherein the first position and the second positionare spaced apart along the stem to permit a robotic hand-off where afirst robot grips the stem at one of the first and second positions anda second robot grips the stem at the other of the first and secondpositions.
 26. The article of manufacture as recited in claim 19,wherein the lens includes a circular shape, the lens attaching to thecold-runner at or below between a 3 o'clock position and a 9 o'clockposition on a face of the lens, the stem extending above the 12 o'clockposition on the lens face.
 27. The article of manufacture as recited inclaim 19, wherein the lens and the cold-runner are formed in a samemolding process.
 28. The article of manufacture as recited in claim 19,wherein the stem is formed during molding, without cutting, to form thefree end portion.
 29. The article of manufacture as recited in claim 19,wherein the lens includes an upper 90-degree quadrant between a 10:30o'clock and a 1:30 o'clock position when the lens is positioned for dipcoating, the stem being connected to the lens outside the upper 90-degree quadrant.
 30. An article of manufacture comprising: a hanger tabhaving a head and a stem all integrally-molded to a plastic lens havingan upper 90 -degree quadrant between a 10:30 o'clock and a 1:30 o'clockposition when the lens is positioned for dip coating, the stem beingedge gated to the lens outside the upper 90 -degree quadrant; and thestem having a second gripping position along its length between the headand the edge gate.
 31. The article of manufacture of claim 30, whereinthe second gripping position of the stem includes a protrudingslide-stop.
 32. The article of manufacture of claim 30, wherein saidstem is configured for mating with a different robotic grip than thehead.
 33. The article of manufacture of claim 30, wherein said stem isconfigured for mating with a different workholder mating geometry thanthe head.
 34. The article of manufacture of claim 30, wherein the headis configured to geometrically mate with a robotic device.
 35. Thearticle of manufacture of claim 30, wherein the head is configured togeometrically mate with a workholder.
 36. The article of manufacture ofclaim 30, wherein the head is configured to geometrically mate with arack.
 37. The article of manufacture of claim 30, wherein the head isconfigured to geometrically mate with a robotic device, a workholder anda rack.
 38. The article of manufacture of claim 30, wherein the head hasa horseshoe shape.
 39. The article of manufacture of claim 38, whereinthe head includes detents to prevent the head from being dislodgedduring transport.
 40. The article of manufacture of claim 30, whereinthe head includes legs which deflect via a pushing force to prevent thehead from being dislodged during transport.
 41. The article ofmanufacture of claim 30, wherein the lens has a top edge when positionedfor dip coating and the head is located above the top edge.
 42. Thearticle of manufacture of claim 41, wherein the second gripping positionis located above the top edge.
 43. The article of manufacture of claim30, wherein the hanger tab rises substantially vertically, when the lensis positioned for dip coating.
 44. The article of manufacture of claim30, further comprising a second lens connected by a cold-runner to theplastic lens, wherein the hanger tab rises off the cold-runner.
 45. Thearticle of manufacture of claim 44, wherein the hanger tab risessubstantially vertically off of the cold-runner, when the lens ispositioned for dip coating.
 46. The article of manufacture of claim 44,wherein the hanger tab is located substantially equidistant between thetwo lenses.
 47. The article of manufacture of claim 46, wherein thehanger tab rises substantially vertically off of the cold-runner, whenthe lenses are positioned for dip coating.
 48. The article ofmanufacture of claim 44, wherein the cold-runner is edge gated to onelens between the 1:30 o'clock and the 4:30 o'clock positions and is edgegated to the other lens between the 7:30 o'clock and 10:30 o'clockpositions, when the lenses are positioned for dip coating.
 49. Anarticle of manufacture comprising: a pair of thermoplastic molded lensesattached by a cold-runner; the cold-runner including a stem with a freeend portion, the free end portion including a point above a highest lensedge when the pair of lenses are held in a dipping position, the freeend portion to provide a first position for a robotic grip, the stemincluding a second position along the length for a robotic grip.
 50. Thearticle of manufacture as recited in claim 49, wherein the free endportion includes a forked head to provide the first position.
 51. Thearticle of manufacture as recited in claim 50, wherein the forked headincludes detents which are configured to receive the robotic grip toprevent dislodging of the forked head during transport.
 52. The articleof manufacture as recited in claim 49, wherein the forked head includeslegs which deflect inwardly to provide a spring force to preventdislodging of the forked head during transport.
 53. The article ofmanufacture as recited in claim 49, wherein the stem includes a bulgedportion to provide the second position.
 54. The article of manufactureas recited in claim 53, wherein the bulged portion extends laterallyoutward from the stem.
 55. The article of manufacture as recited inclaim 49, wherein the first position and the second position are spacedapart along the stem to permit a robotic hand-off where a first robotgrips the stem at one of the first and second positions and a secondrobot grips the stem at the other of the first and second positions. 56.The article of manufacture as recited in claim 49, wherein each lensincludes a circular shape, each lens attaching to the cold-runner at orbelow between a 3 o'clock position and a 9 o'clock position on a face ofthe lens, the stem extending above the 12 o'clock position on the lensfaces.
 57. The article of manufacture as recited in claim 49, whereinthe lens and the cold-runner are formed in a same molding process. 58.The article of manufacture as recited in claim 49, wherein the stem isformed during molding, without cutting, to form a hanger tab portion.59. The article of manufacture as recited in claim 49, wherein each lensincludes an upper 90-degree quadrant between a 10:30 o'clock and a 1:30o'clock position when the lens is positioned for dip coating, the stembeing connected to the lens outside the upper 90 -degree quadrant.
 60. Amethod for manufacturing lenses, comprising the steps of: molding a pairof thermoplastic molded lenses attached by a cold-runner, thecold-runner including a stem with a free end portion, the free endportion including a point above a highest lens edge when the pair oflenses are held in a dipping position, the free end portion to provide afirst position for a robotic grip, the stem including a second positionalong the length for a robotic grip; gripping one of the first positionand the second position to provide a gripped position; and dip coatingthe lens pair by immersing the lens pair in solution without immersingthe gripped position.
 61. The method as recited in claim 60, wherein thestep of molding includes injection-molding polycarbonate.
 62. The methodas recited in claim 60, wherein the free end portion includes a forkedhead to provide the first position, the forked head including detentswhich are configured to receive the robotic grip, and wherein the stepof gripping includes gripping the forked head at the detents to preventdislodging of the forked head during transport.
 63. The method asrecited in claim 60, wherein the free end portion includes a forked headto provide the first position wherein the forked head includes legswhich deflect inwardly to provide a spring force wherein the step ofgripping includes gripping the forked head while compressing the legs toprevent dislodging of the forked head during transport.
 64. The methodas recited in claim 60, wherein the stem includes a bulged portion toprovide the second position, and the step of gripping includes grippingthe stem below the bulged portion.
 65. The method as recited in claim60, wherein the first position and the second position are spaced apartalong the stem, and further comprising the step of handing-off thelenses between robot grips where a first robot grips the stem at one ofthe first and second positions and a second robot grips the stem at theother of the first and second positions.
 66. The method as recited inclaim 60, wherein the step of dip coating the lens pair includesmaintaining the first position above a surface of the solution duringthe dip coating.
 67. The method as recited in claim 60, wherein the stepof dip coating the lens pair includes maintaining the free end portionabove a surface of the solution during the dip coating while the pair oflenses are fully immersed in the solution.
 68. The method as recited inclaim 60, wherein the step of dip coating the lens pair includesmaintaining the free end portion vertically above the lenses during thedip coating.
 69. The method as recited in claim 60, wherein thecold-runner attaches to each lens at or below between a 3 o'clockposition and a 9 o'clock position on a face of the lens, and wherein thestep of dip coating the lens pair includes maintaining the free endportion vertically above the lenses during the dip coating.
 70. Themethod as recited in claim 60, wherein the step of molding includesforming the pair of lenses and the cold-runner in a same moldingprocess.
 71. The method as recited in claim 60, wherein the stem isformed during molding, without cutting, to form a hanger tab portion.72. The method as recited in claim 60, wherein the steps of molding,gripping and dip coating are performed in a same clean-room envelope.73. The method as recited in claim 60, further comprising the step ofcuring the dip coating material.
 74. The method as recited in claim 60,further comprising the step of coating the each lens with ananti-reflection coating.
 75. The method as recited in claim 60, furthercomprising the step of inspecting the pair of lenses in an automaticinspection process.
 76. The method as recited in claim 75, wherein thestep of inspecting is carried out in a same clean-room envelope as thesteps of molding, gripping and dip coating.
 77. The method as recited inclaim 60, wherein the first position includes a hanger tab which extendsbeyond a highest lens edge vertically above a coating solution duringthe dip coating step.
 78. The method as recited in claim 60, wherein thecold-runner attaches to each lens outside of an upper 90 -degreequadrant between a 10:30 o'clock position and a 1:30 o'clock positionwhen the lens is positioned for dipping, and wherein the step of dipcoating the lens includes maintaining the free end portion verticallyabove the lens during the dip coating.
 79. The method as recited inclaim 60, wherein the free end portion includes a point above a highestlens edge when the lens is held during the step of dip coating.
 80. Themethod as recited in claim 60, wherein said molding step includesmolding two lenses connected by the cold-runner, wherein the stem risesoff the cold-runner.
 81. The method as recited in claim 80, wherein thestem rises substantially vertically off of the cold-runner, when thelens is positioned for dip coating.
 82. The method as recited in claim80, wherein the stem is located substantially equidistant between thetwo lenses.
 83. A method for manufacturing lenses, comprising the stepsof: molding a thermoplastic molded lens with a cold-runner attached tothe lens, the cold-runner including a stem with a free end portion, thefree end portion including a point above a highest lens edge when thelens is held in a dipping position, the free end portion to provide afirst position for a robotic grip, the stem including a second positionalong the length for a robotic grip; gripping one of the first positionand the second position to provide a gripped position; and dip coatingthe lens by immersing the lens in solution without immersing the grippedposition.
 84. The method as recited in claim 83, wherein the step ofmolding includes injection-molding polycarbonate.
 85. The method asrecited in claim 83, wherein the free end portion includes a forked headto provide the first position, the forked head including detents whichare configured to receive the robotic grip, and wherein the step ofgripping includes gripping the forked head at the detents to preventdislodging of the forked head during transport.
 86. The method asrecited in claim 83, wherein the free end portion includes a forked headto provide the first position wherein the forked head includes legswhich deflect inwardly to provide a spring force wherein the step ofgripping includes gripping the forked head while compressing the legs toprevent dislodging of the forked head during transport.
 87. The methodas recited in claim 83, wherein the stem includes a bulged portion toprovide the second position, and the step of gripping includes grippingthe stem below the bulged portion.
 88. The method as recited in claim83, wherein the first position and the second position are spaced apartalong the stem, and further comprising the step of handing-off the lensbetween robot grips where a first robot grips the stem at one of thefirst and second positions and a second robot grips the stem at theother of the first and second positions.
 89. The method as recited inclaim 83, wherein the step of dip coating the lens includes maintainingthe first position above a surface of the solution during the dipcoating.
 90. The method as recited in claim 83, wherein the step of dipcoating the lens includes maintaining the free end portion above asurface of the solution during the dip coating while the lens is fullyimmersed in the solution.
 91. The method as recited in claim 83, whereinthe step of dip coating the lens includes maintaining the free endportion vertically above the lens during the dip coating.
 92. The methodas recited in claim 83, wherein the cold-runner attaches to the lens ator below between a 3 o'clock position and a 9 o'clock position on a faceof the lens, and wherein the step of dip coating the lens includesmaintaining the free end portion vertically above the lens during thedip coating.
 93. The method as recited in claim 83, wherein the step ofmolding includes forming the lens and the cold-runner in a same moldingprocess.
 94. The method as recited in claim 83, wherein the stem isformed during molding, without cutting, to form a hanger tab portion.95. The method as recited in claim 83, wherein the steps of molding,gripping and dip coating are performed in a same clean-room envelope.96. The method as recited in claim 83, further comprising the step ofcuring the dip coating material.
 97. The method as recited in claim 83,further comprising the step of coating the lens with an anti-reflectioncoating.
 98. The method as recited in claim 83, further comprising thestep of inspecting the lens in an automatic inspection process.
 99. Themethod as recited in claim 98, wherein the step of inspecting is carriedout in a same clean-room envelope as the steps of molding, gripping anddip coating.
 100. The method as recited in claim 83, wherein the firstposition includes a hanger tab which extends beyond a highest lens edgevertically above a coating solution during the dip coating step. 101.The method as recited in claim 83, wherein the cold-runner attaches toeach lens outside of an upper 90 -degree quadrant between a 10:30o'clock position and a 1:30 o'clock position when the lens is positionedfor dipping, and wherein the step of dip coating the lens includesmaintaining the free end portion vertically above the lens during thedip coating.
 102. The method as recited in claim 83, wherein the freeend portion includes a point above a highest lens edge when the lens isheld during the step of dip coating.
 103. The method as recited in claim83, wherein said molding step includes molding two lenses connected bythe cold-runner, wherein the stem rises off the cold-runner.
 104. Themethod as recited in claim 103, wherein the stem rises substantiallyvertically off of the cold-runner, when the lens is positioned for dipcoating.
 105. The method as recited in claim 103, wherein the stem islocated substantially equidistant between the two lenses.